Connective Technologies
Wind Turbines Australia
Solar Panels
SOLAR ARRAYS COMMERCIAL OR DOMESTIC
At Times you may need solar power to your factory taking some of the power off grid that you are using, this is reasonably easy to do, just call our sales team for a quote,
if you are a warehouse and you are using only a small amount of power it is very easy to have your warehouse taken off the grid and be self sufficient in power. depending on your power usage some warehouse owners say its not worth the cost for solar and the change over, I beg to differ, our power accounts will double over the next 5 years as they have increased in cost by 69.4% in one year in NSW, and are due to go up by 10% in January 2013.
Commercial array
Domestic
13.720Kw Solar Array
The output of a solar array depends on the type of panels used, the amount of sunshine, temperature, orientation and atmospheric conditions. As a guide, a 1kW [1000W] solar array installed in an unobstructed sunny position in Melbourne will produce an average daily output as follows:
· polycrystalline solar array 3.5kWh/day
· monocrystalline solar array 3.7kWh/day
· amorphous solar array 4.4kWh/day
Not all electricity produced by an array is available to the grid, There is small cabling losses and also losses in the inverter. These figures quoted an allowance of 10% to cover losses.
An array is sized according to the amount of electricity required, subject to constraints such as budget and available roof space. There may also be some technical and administrative constraints applicable and these are mentioned below.
The array comprises a number of interconnected and usually identical solar panels. The panels typically have a nameplate rating of between 64W and 160W and have a nominal voltage of either 12V or 24V. The operating voltage of each panel is determined by the inverter, which continuously adjusts the voltage of the array so as to yield maximum output.
The peak power voltage depends on the intensity of the sunlight and also on temperature. For a nominal 12V panel it typically lies between 15V and 17V, for a nominal 24V panel the values are 30V to 36V.
The solar panels are connected together in series to form one or more strings. The voltage of each string is the sum of its individual panel voltages. The number of panels in each string is chosen so that the peak power voltage of the entire string suits the inverter. This value is usually between 85V and 180V.
Some solar panels designated specifically for grid-connect applications have much higher peak power voltages, being about 70V. They offer an advantage of requiring fewer panels per string, but in other respects have similar properties to nominal 12V or 24V panels
Mounting and Orientation
The solar array needs to be securely installed, able to withstand wind and other loads and as far as possible face the sun. The three methods described here are roof frames, solar roof tiles and ground frames.
The most common method is to mount the solar panels on frames attached to the roof of a building. If the roof faces north, the panels can lie almost flat on the roof. In fact, the panels are raised a few centimetres off the roof to allow ventilation and not obstruct the flow of water.
A more common method is to provide the frame with legs so that the array is mounted at an angle to the roof. This is particularly effective on a gently sloping south facing roof as it allows winter sun to be reflected off the roof onto the panels in addition to direct radiation. As far as possible north or south facing roofs are chosen, this being consistent with the design principle of aligning dwellings so that the long side of the building runs east-west.
Solar tiles allow the array to become part of the roof, being fixed directly to battens in place of conventional tiles. Monocrystalline 75W and 85W solar tiles are commercially available for this purpose.
Ground mounted frames are used where the roof is too steep, shaded or otherwise unsuitable. Ground mounted arrays have the disadvantage of being more expensive than roof frames and taking up garden space. Any ground frame needs to be certified by a qualified engineer.
Usually solar arrays are mounted in a fixed position and are not adjusted to allow for the daily or seasonal movement of the sun. This is especially so for roof mounted arrays. Nevertheless tracking systems are available, however this topic lies outside the scope of these notes.
For grid connected solar systems, the array is oriented so as to maximise the expected average yearly output. For Cairns and the Tablelands the optimum orientation is facing north, tilted at an angle of between 14 deg. and 17 deg. from horizontal. This is different from arrays for stand- alone systems where the tilt is about 30 deg. in order to improve winter performance.
Solar panels are installed differently based on their geographic locations throughout the world. The premise behind this is simple; the sun is in a different place in the sky, so panels need to be directed according to this positioning. The ideal situation is when the sun is hitting the panels at a perfectly perpendicular angle (90°). This maximizes the amount of energy striking the panels and being produced. The two factors that such an angle is controlled by are the orientation (North/South/East/West) and the angle of the panels from the surface of the Earth. So in Australia, what angle and orientation are best?
Tilting
The tilt involves primarily the angle that the panels are facing up into the sky. On a flat roof, the tilt is 0°, whereas if the angles were to be facing a wall, it would be 90°. As indicated in the above diagram, an angle of approximately 32° is the best, but anywhere between 20° and 40° is optimal for around a 90% efficiency. As soon as a panel is tilted below 5°, efficiency will become an issue, as well as if it is placed at an angle larger than 60°. All in all, tilting is an important factor, but not as important as the orientation can be.
Orientation
Australia, being in the Southern Hemisphere, experiences a sun that is predominantly coming at us from the North. There is of course deviance throughout the seasons, but ideally solar panels should be facing as close to true North as possible to reduce the impact that the Winter seasons have on efficiency. Once again referring to the graph above, one can see that even North Easterly and North Westerly facing panels will be largely operating at around the 90% of their rated outputs. Once angles start approach that East North East or West North West orientation however, the numbers start reducing rapidly. A directly East or West facing panel will never operate at better than 85% of its rated output.
